ANATOMY AND LIFE HISTORY OF MOLLUSCA. 161 



is so conspicuous, though it is not as a matter of fact so common 

 as represented. But the difficulty really was to see and distinguish 

 them. They are dirty dull green shells, looking as if they had 

 been stranded on the withered corals by a very muddy tide. No 

 one would suspect the existence of the beautiful pattern underneath, 

 and this is true of all the cones, the Strombidse or wing-shells, and 

 in fact of all the tropical beauties except the porcellanous cowries 

 and a few others. What covers the shell is a periostraca of living 

 tissue, a very perishable material which can only be studied when 

 the shell is taken fresh from the sea. It soon perishes if allowed 

 to dry ; and spirit, or indeed any preserving fluid that has been 

 devised as yet, so alters the structures in the course of time that 

 it interferes to some extent at least with the condition of the 

 tissues, and prevents their recognition. 



Now it cannot be too often insisted upon, that in this external 

 covering, any sense-organs which are possessed by the animal will 

 be found to exist. A little reflection must convince us, for instance 

 that the provisions for sight which are found on the tentacles of 

 the animal can be of no use except for guidance in walking and 

 taking food. The animal and the interior of its shell must 

 remain absolutely in darkness, and worse off in point of seeing 

 than any of the molluscan beings in the animal kingdom. The 

 discovery by Mr. Mosely of the eyes in Chiton shows us that some 

 other provision exists, and that vision is given to these animals on 

 an extremely liberal scale. It would be a most singular thing in 

 nature if the Chitonidse were the only family where such sense- 

 organs existed. I can well understand however that a search will 

 be often unsuccessfully made upon shells by those who wish to 

 follow up the observations of Mr. Mosely. But does the observer 

 know what has happened to his shell before it came into his 

 possession ? The periostraca and all the living external tissues 

 have been roughly stripped off, and it has been scrubbed and 

 brushed and scoured till the hard and durable shell-substance has 

 alone remained. It has been cleansed with acids besides a liberal 

 alkaline cleansing by means of soap-suds &c. In nine cases out 

 of ten, oriental shells are collected in India and the Indian 

 Archipelago by the natives, who leave them in the sun for the 

 animal to rot out of them and the shell to be bleached by the sun. 

 They are then again soaked in sea-water to remove the decomposed 

 tissues and the odoriferous properties. It is no wonder therefore 

 that if there were eyes or any other organs they have hitherto 

 escaped observation, nor will they be recognized until the shell on 

 the living animal is studied in every case. 



Anatina tasmanica, Reeve, is an ovate, translucent widely* 

 gaping shell, about an inch and a-half in length, and half that 

 width, with a peculiar split near the umbones like all the members. 



K-July 4, 1888. 



